1. Field of the Invention
This invention relates generally to charge transfer device arrays and more particularly to charge transfer device registers into which a background (fat zero) signal level, equal to about 10 percent of the maximum signal, is introduced. The circuit of the invention may be used with any charge transfer device array, such as a bucket brigade or a charged transfer coupled device array.
2. Description of the Prior Art
Various techniques are known for providing initial charge level for time variant or analog signals in charge transfer technology devices, i.e. bucket brigade and charge coupled device circuits.
In U.S. Pat. No. 3,911,290 assigned to the same assignee as the present invention there is shown a bucket brigade circuit which although directed toward a shift register in which each storage capacitance shift register can be used to store information portrays a typical prior art input circuit including an input bias voltage gating device and capacitance.
In U.S. Pat. No. 3,801,826 there is taught the generation of a zero charge input level through the use of a diode for charging the input node to a reference level one threshold less than that of the clock levels.
U.S. Pat. No. 3,899,694 teaches the generation of bias reference voltage for charge transfer registers which are a function of device threshold.
U.S. Pat. No. 3,831,041 also teaches various additional circuits for providing bias voltages for such charge transfer devices.
U.S. Pat. No. 4,130,766 also assigned to the same assignee as the present invention, teaches a method for cancelling charge out-coupling from the first stage of a bucket brigade circuit by capacitivly coupling in an equal charge thus establishing the zero level of the charge in the first stage as a function of input voltage.